At present there are two methods in joining the dirt entrance with the upper layer of unwoven cloth for a dust buster filter for a vacuum cleaner. One is to join them directly together by sewing, and the other is to join them together by furing them together by means of high frequency. But there is no cylindrical protrusions on the back surface of the dirt entrance, or small holes on the upper layer of unwoven cloth for firmly joining the both together. However, a dust buster filter has to withstand the force of blown air coming from a blower and to keep dirt therein it is quite important that the plastic section of the filter body is firmly joined with the upper layer of the filter body such that the both do not separate from each other under the strong blowing force.
The joining methods just mentioned above have the following shortcoming.
1. The sewing method causes bad outward appearance and the thread sewn may be often broken owing to moisture so that the both, the dirt entrance and the filter body, can lose their function, separated from each other.
2. The fusing method with high frequency or super-sonic wave costs high for mass production because of expensiveness of its equipment.
Therefore, this invention has been devised, based upon several years' experience by improving the joining method in manufacturing dust buster filter for a vacuum cleaner.